The present invention generally relates to switches. In particular, the present invention relates to flow switches which are useful as a component of a high pressure washing system and other systems where the stoppage of flow could be used to trigger an action.
In high pressure washing systems, water is heated in water heater tanks by burners. The burners must be regulated so that the water does not become too hot, otherwise the water heater tanks can be in danger of exploding. One method of regulating the water heating subsystem of a high pressure washing system was by using a pressure switch. A pressure switch flips between its xe2x80x9coffxe2x80x9d and xe2x80x9conxe2x80x9d positions depending on whether there is pressure present in the water pipe leading out of the water heater tank. When pressure was present, the pressure switch allowed the burners to operate. When pressure was removed, the pressure switch turned off the burners.
Regulating the burners with a flow switch rather than a pressure switch is another method that is used in the industry. A flow switch senses flow rather than pressure. Thus, while a customer is using the washing system, a flow switch can sense the flow of water through the system and can turn on the burners during this time. When the customer releases the trigger on the washer""s wand, the water flow ceases and the flow switch can be used to turn the burner off.
Known flow switches in the high-pressure washing system industry are reed-type switches. In such a reed switch, a piston within a water pipe is spring loaded. While water is flowing through the pipe, the water pressure against the piston compresses the spring, causing the piston to be located at a certain position within the pipe. Once the water pressure is relieved, the piston is no longer pressed against the spring, and so the spring decompresses, moving the piston back to its resting position. The piston within the pipe is fitted with a magnet. The reed switch sensor is installed exterior to the water pipe, parallel to the piston""s axis of movement. The metal reed switch sensor opens or closes depending on the piston""s position within the pipe.
Such reed switches have their disadvantages. Foremost, to protect the switch, the reed switch is placed in a sealed glass capsule-like container. Glass is needed because of its magnetically neutral properties. The glass container may be housed in a thin brass sleeve for attachment to the water pipe. Of course, the glass container is prone to breakage. In fact, the glass container is sometimes damaged even during shipping. If shipping doesn""t break the glass container, installing the switch can break it. Often, the reed switch within the glass container is installed to the brass sleeve or water pipe with a set screw. If this set screw is overly tightened, the glass container breaks. Even after installation, a reed switch remains prone to breakage from undue vibrations in the water pipe or by carelessness of maintenance workers when working near the switch.
Another disadvantage of the reed switches is the calibration needed during installation. The reed switch within its glass container opens and closes based on a magnetic field from the magnet on the piston within the water pipe. On installation, the reed switch must be positioned very precisely so that the switch will open and close properly. If the switch is not calibrated correctly against the piston""s magnet, the switch will not be able to correctly sense the flow of water through the pipe. Each time the reed switch is replaced, this calibration must be repeated.
A final disadvantage to some of the current flow switches is the pressure drop associated with using the switch. Some current switches can cause a pressure drop of between 30 and 45 p.s.i. when the flow rate is at 7 gallons per minute. This pressure drop is an inefficiency that makes a washing system utilizing such switches less desirable.
It would be desirable to manufacture a switch that alleviates the disadvantages of the current flow switches. It would be desirable to have such a switch not encased in glass or other fragile material so that the switch could be quite dependable and rugged. It would also be desirable to have the switch capable of being installed easily, with fewer calibration issues. Finally, the switch should cause minimal pressure drop.
The present invention is a in-line flow switch for a high-pressure washing system or other flow-related system. The in-line flow switch is normally in the open position, but is moved to the closed position by the flow of water or other fluid through a pipe.
The in-line flow switch includes a housing and a cartridge. The cartridge is made up of a plunger retainer, a plunger, an actuator magnet, a spring, a face seal washer, a sensor, and a cartridge body.
The in-line flow switch advantageously is made up of inexpensive, durable materials, without the need for a reed switch""s use of glass. All of the moving parts to the in-line flow switch are packaged in a single cartridge which is advantageous for maintenance; if the in-line flow switch should fail, the entire switch can be quickly and easily replaced by disconnecting the faulty in-line flow switch cartridge and replacing it with a new in-line flow switch cartridge. Another advantage of the present invention is that when the in-line flow switch is installed, the calibration procedure needed with prior reed switches is eliminated.